I just replaced my oil pressure switch and I think it defective I need help unless I messed up the wiring or something

 

Welcome to the forum!
It helps us if you list year, make, model, motor, etc
Also, why did you change the sender - what was it doing before the switch?

 

Its a 1996 chevy silverado rwd 5.0 and it wasnt reading correctly before.... the light to check it would always come on "check gauges" when i would be driving long distances it would read 40 while driving but once I was idleing it would drop to 0 and the light would pop on ; I am going to get a replacement just incase I got a defective switch so tomorrow Ill be able to know more hopefully

 

Most units will go all the way over to the end if the wire bringing the signal is grounded.
If unplugged, and the key is on some will go all the way back or read -40..(minus 40).